In the course of an investigation on the synthesis of optically active eremophilane sesquiterpenoids from sabinene, A. van der Gen et al. [Rec. Trav. Chim. PaysBas, 90, 1034 (1971)] synthesized a compound to which they attributed the structure of trans-10,10-dimethyl-tricyclo[7.1.1.0.sup.2,7 ]undec-2-en-4-one. No indication as to the properties of this ketone was however given by the cited authors, nor any suggestion was formulated by them concerning its possible use as perfume or flavour ingredient. We have now found that cis-10,10-dimethyl-tricyclo[7.1.1.0.sup.2,7 ]undec-2-en-4-one possesses useful organoleptic properties and consequently it can advantageously be used in the perfume and flavour industry.